The present invention is directed to a hand-held power tool, in particular a rotary hammer.
With a known hand-held power tool designed as a rotary/chisel hammer, the tool fitting is fixedly connected with a rotary or drive sleeve that is drivable in a rotatory manner by a driven wheel of a drive transmission situated on the rotary sleeve. The tool held in the tool fitting in an axially limited, displaceable manner is acted upon in the axial direction by an impact mechanism that impacts the shank end of the tool in a pulsed manner via a ram or a beatpiece. The hand-held power tool is selectively operable in the “impact drilling” mode or the “chiseling” mode. The tool is acted upon by the impact mechanism in both modes. In the “impact drilling” mode, in which an impact drill is inserted in the tool fitting, the tool fitting and, therefore, the tool are driven in a rotatory manner. In the “chiseling” mode, in which a chiseling tool is inserted in the tool fitting, the tool fitting is non-rotatably fixed to the mounting housing, and the chiseling tool only makes a hammering motion via the action of the impact mechanism. A duty-type switch is used to switch between modes, the switch including a manually operated rotary knob and an engaging fork capable of being displaced by the rotary knob. A coupling ring is installed on the engaging fork, the coupling ring fixedly coupling the rotary sleeve with the driven wheel of the drive transmission in a first displacement position and, in a second displacement position, fixedly joining the rotary sleeve with the machine housing. In an intermediate position, the coupling ring engages with neither the driven wheel nor the machine housing, so that the rotary sleeve and, therefore, the tool fitting, are free to rotate without being driven.
In the case of hand-held power tools with a rotating tool, operator errors, work piece faults or destruction of the tool can cause forces to act on the hand-held power tool that the operator is unable to control and, under certain circumstances, can result in injury to the operator.
In the case of a known hand-held power tool with a rotating tool (EP 0 771 619 B1), a system is installed with which uncontrolled jamming is detected and the resultant rotational motion of the machine housing is braked and limited. The system includes a sensor that detects the movement quantity that characterizes the special dimensions of the hand-held power tool as a whole, e.g., acceleration, rotational speed, or rotational travel of the machine housing, an operator that generates a control signal when a predefined threshold value of the movement quantity supplied by the sensor is reached or exceeded, and an actuator that interrupts the drive for the rotating tool based on the control signal from the operator. The actuator is designed as a separating clutch in the drive train of the tool and/or as a switch for turning off the drive motor and/or as a clutch for abruptly connecting the drive train with the machine housing.